Field of the Invention and Related Background Art
This invention relates to a process for disintegrating silica fine powder, particularly to a process for disintegrating silica fine powder with primary particle sizes of 1.mu. or less.
Fine powder, particularly fine powder with primary particle sizes of 1.mu. or less, is itself susceptible to agglomeration and extremely rarely exists as primary particles. When such fine powder is used for various additives, if it is in an agglomerated state, performances as fine powder cannot be exhibited to bring about lowering in efficiency. For this reason, it has been desired to have a method for disintegrating such agglomerate of fine powder.
In the prior art, as the disintegrating method of fine powder, there have been known the method in which fine powder is treated under the conditions to the extent which do not crush the particles by controlling the operational conditions of a pulverizer such as the jet mill or impact system pulverizer.
However, in such method, although disintegrating is possible when the agglomerated mass of fine powder is large, or when the true specific gravity of fine powder is large, it is difficult to perform disintegration sufficiently when the size of the agglomerated mass is several 10 .mu.m or less as in the case of silica fine powder or when the apparent density is small as in the case of silica fine powder.
Particularly, it is very difficult to disintegrate fine powder with very strong agglomerating tendency with primary particle sizes of 0.1.mu. or less such as silica fine powder according to the conventional method.
There is also a method for disintegrating fine powder by use of a medium as in the ball mill, but in this case, a long time is required, whereby there is the tendency that grinding by rubbing mutually between media is generated to entrain impurities into fine powder undesirably. Further, in the case of the ball mill, it is disintegration in a nonuniform system and may sometimes form a new agglomerated product undesirably. Otherwise, a mixing device can be also used as the disintegrator, but in the ordinary mixing device, it is difficult to obtain sufficient disintegration due to weak shearing force.